JP6922651B2 - Ultrasonic device and ultrasonic measuring device - Google Patents

Description

The present invention relates to an ultrasonic device and an ultrasonic measuring device.

Conventionally, an ultrasonic device that outputs an ultrasonic wave to an object is known (see, for example, Patent Document 1). The ultrasonic device (ultrasonic sensor) described in Patent Document 1 has a diaphragm (membrane) formed by etching a part of a support layer, and a lower electrode, a piezoelectric film, and an upper electrode laminated on the diaphragm. It is provided with a piezoelectric laminate. Then, in this ultrasonic device, a thin film of fluorocarbon is provided so as to cover the surface of the diaphragm on the side where the piezoelectric laminate is provided.
In such an ultrasonic device, a voltage is applied to the lower electrode and the upper electrode of the piezoelectric laminate to vibrate the diaphragm, and the vibration of the diaphragm acts directly on the air to generate a compressional wave, thereby generating ultrasonic waves. Is transmitted into the air. Therefore, in such an ultrasonic device, it is not necessary to separately provide a layer (acoustic matching layer) or the like for matching the acoustic impedance, and the configuration can be simplified.

Japanese Unexamined Patent Publication No. 2010-183437

However, if the diaphragm is configured to vibrate independently, the Q value of the diaphragm itself becomes high, making it difficult to control the transmission and reception of ultrasonic waves, and the reverberation vibration (tailing of vibration) after transmitting ultrasonic waves also becomes long. However, there is a problem that the transmission / reception accuracy of ultrasonic waves is lowered.

An object of the present invention is to provide an ultrasonic device having high accuracy in transmitting and receiving ultrasonic waves, and an ultrasonic measuring device.

The ultrasonic device according to an application example of the present invention includes a vibrating membrane having a vibrating region capable of vibrating by a vibrating element, and a damper layer provided so as to cover the vibrating region of the vibrating membrane. The thickness dimension of is 13 μm or more and 25 μm or less.

In this application example, the vibrating membrane is provided with a vibrating region capable of vibrating by a vibrating element, and a damper layer having a thickness dimension of 13 μm or more and 25 μm or less is provided at a position covering the vibrating region.
Here, when the thickness dimension of the damper layer provided on the vibrating film exceeds 25 μm, the vibration in the vibration region is hindered by the damper layer. In this case, when transmitting ultrasonic waves, the vibration region cannot vibrate with sufficient displacement, and the transmission sensitivity of ultrasonic waves (sound pressure of ultrasonic waves) decreases. In addition, when receiving ultrasonic waves, the displacement of the vibrating membrane due to the received ultrasonic waves is reduced, so that the receiving sensitivity is also lowered. Further, when the thickness dimension of the damper layer provided on the vibrating membrane is less than 13 μm, the reverberation vibration (tailing of vibration) when the vibration region vibrates becomes long, and the transmission / reception accuracy of ultrasonic waves is lowered.
On the other hand, as described above, when a damper layer having a thickness of 13 μm or more and 25 μm or less is provided, vibration inhibition in the vibration region by the damper layer is suppressed, so that the transmission / reception sensitivity of ultrasonic waves can be increased. can. In addition to this, the damper layer can also suppress the occurrence of reverberation vibration and improve the transmission and reception accuracy of ultrasonic waves. Further, since the damper layer is provided on the vibrating membrane, the Q value of the vibrating membrane itself can be reduced, so that the control related to the transmission and reception of ultrasonic waves becomes easy.

In the ultrasonic device of this application example, the damper layer is preferably made of a material having a Young's modulus of 150 MPa or less.
In this application example, the Young's modulus of the damper layer is 150 MPa or less. When a layer made of, for example, a fluorocarbon film or a material having a high Young's modulus such as polytetrafluoroethylene (PTFE) is formed as the damper layer, the damper layer inhibits the vibration in the vibration region. On the other hand, by using the damper layer having the Young's modulus as described above, the inconvenience that the vibration in the vibration region is hindered can be suitably suppressed.

In the ultrasonic device of this application example, the vibrating element includes a lower electrode provided on one surface of the vibrating film, a piezoelectric layer laminated on the lower electrode, and an upper electrode laminated on the piezoelectric layer. It is a piezoelectric element, and the damper layer is preferably provided on the one surface of the vibrating film on which the piezoelectric element is provided.
In this application example, the vibrating element is composed of a lower electrode, a piezoelectric layer, and a piezoelectric element in which an upper electrode is laminated. In such a piezoelectric element, the piezoelectric layer can be deformed by applying a voltage between the lower electrode and the upper electrode, and the deformation of the piezoelectric layer vibrates the vibration region to transmit ultrasonic waves. be able to. Further, when ultrasonic waves are input to the vibration region of the vibrating membrane, the vibration region is displaced. As a result, a potential difference corresponding to the displacement amount of the piezoelectric layer provided in the vibration region is generated between the lower electrode and the upper electrode, and the reception of ultrasonic waves can be detected by detecting this potential difference.
Then, in this application example, the damper layer is provided on the side where the piezoelectric layer of the vibrating membrane is arranged. That is, the piezoelectric element is covered with the damper layer, and the piezoelectric element can be protected. For example, it is possible to suppress the occurrence of burning of the piezoelectric layer due to the adhesion of water droplets to the piezoelectric layer.

In the ultrasonic device of this application example, the damper layer is the first direction of the vibrating film, with the direction in which ultrasonic waves are transmitted when the vibrating element vibrates the vibrating region as the first direction. It is preferably provided on the opposite surface.
When transmitting ultrasonic waves into the air by the ultrasonic device of this application example, if a damper layer is provided on one surface of the vibrating membrane on the side of the ultrasonic wave transmission direction (first direction), the ultrasonic waves form the damper layer. It will be transmitted into the air via. In this case, the ultrasonic wave is attenuated by the damper layer. On the other hand, in this application example, since the damper layer is provided on the side opposite to the first direction of the vibrating membrane, the ultrasonic waves can be transmitted into the air without being attenuated, and the ultrasonic waves can be transmitted into the air. Sound waves can be received in the vibration region without being attenuated.

The ultrasonic measuring device of one application example according to the present invention is characterized by including an ultrasonic device as described above and a control unit for controlling the ultrasonic device.
In this application example, as described above, the provision of the damper layer in the ultrasonic device facilitates the transmission / reception control of ultrasonic waves. Further, since the vibration in the vibration region is not hindered by the damper layer, the transmission / reception sensitivity of ultrasonic waves can be increased, and the reverberation vibration can also be suppressed, so that high-precision ultrasonic transmission / reception processing can be performed. Can be carried out.
Therefore, in the ultrasonic measuring device, the control unit can easily control the ultrasonic device and can transmit and receive ultrasonic waves with high transmission / reception accuracy, so that the ultrasonic measurement is performed with high accuracy. be able to.

The plan view which shows the schematic structure of the ultrasonic device of 1st Embodiment. FIG. 3 is a cross-sectional view of a part of the ultrasonic device of the first embodiment. The figure which shows the relationship between the thickness dimension of a damper layer in an ultrasonic device, and the maximum displacement amount of a vibrating part. The figure which shows the pulse width by the reverberation vibration when the damper layer is not provided. The figure which shows the pulse width by the reverberation vibration when the damper layer of a thickness dimension of 20 μm is provided. It is a figure which shows the relationship between the thickness dimension of a damper layer, and the pulse width when the width dimension of an opening is 170 μm, 200 μm, 260 μm. FIG. 6 is a diagram showing a change in pulse width when the thickness dimension of the damper layer is 0 as a reference (100%). The figure which shows the relationship between Young's modulus of a damper layer and deformation efficiency of the vibration amplitude of a vibrating part. The figure which shows the schematic structure of the distance sensor which concerns on 2nd Embodiment. The cross-sectional view which shows the schematic structure of the ultrasonic device which concerns on the modification of 1st Embodiment. FIG. 5 is a cross-sectional view showing a schematic configuration of an ultrasonic device according to another modification of the first embodiment.

[First Embodiment]
Hereinafter, the ultrasonic device according to the first embodiment of the present invention will be described. FIG. 1 is a plan view showing a schematic configuration of the ultrasonic device 10. FIG. 2 is a cross-sectional view of a part of the ultrasonic device 10 when the line AA of FIG. 1 is cut.
As shown in FIGS. 1 and 2, the ultrasonic device 10 includes an element substrate 11, a piezoelectric element 12, and a damper layer 13 (see FIG. 2). Here, in the following description, the substrate thickness direction of the element substrate 11 is the Z direction, and the biaxial directions orthogonal to the Z direction are the X direction and the Y direction, respectively. Further, the Z direction (direction toward the + Z side) corresponds to the first direction of the present invention and is a direction for transmitting ultrasonic waves.

(Structure of element substrate 11)
As shown in FIG. 2, the element substrate 11 includes a substrate main body 111 and a vibrating film 112 provided on the −Z side of the substrate main body 111.
The substrate main body 111 is a substrate that supports the vibrating film 112, and is composed of, for example, a semiconductor substrate such as Si. Here, as shown in FIG. 1, the element substrate 11 is provided with a plurality of openings 111A arranged in a two-dimensional array along the X and Y directions in a plan view from the Z direction. There is.
In the present embodiment, each opening 111A is a through hole penetrating the substrate thickness direction (Z direction) of the substrate main body 111, and the vibrating film 112 closes one end side (−Z side) of the through hole. Is provided.

The vibrating film 112 is composed of, for example, SiO ₂ , _{a laminated body of SiO 2} and ZrO ₂ , and is provided on the −Z side of the substrate main body 111. The thickness of the vibrating film 112 is sufficiently smaller than that of the substrate main body 111. The vibrating film 112 is supported by the wall portion 111B (see FIG. 2) of the substrate main body portion 111 constituting the opening portion 111A, and closes the −Z side of the opening portion 111A. A portion of the vibrating membrane 112 that overlaps the opening 111A in a plan view (a region that closes the opening 111A) constitutes the vibrating portion 112A. That is, the opening 111A defines the outer edge of the vibrating portion 112A of the vibrating membrane 112. The vibrating portion 112A is a vibrating region that can be vibrated by the piezoelectric element 12.

(Structure of Piezoelectric Element 12)
The piezoelectric element 12 is the vibrating element of the present invention, and in the present embodiment, it is located on one surface (the surface on the −Z side) of the vibrating film 112 and at a position where it overlaps with each vibrating portion 112A in a plan view from the Z direction. Each is provided. As shown in FIG. 2, the piezoelectric element 12 is configured by sequentially laminating a lower electrode 121, a piezoelectric layer 122, and an upper electrode 123 on a vibrating film 112.

Specifically, as shown in FIG. 1, the lower electrode 121 is formed linearly along the X direction. Both ends (± X side ends) of the lower electrode 121 are, for example, lower electrode terminals 121P connected to a circuit board or the like that controls the ultrasonic device 10.
Further, the upper electrode 123 is formed linearly along the Y direction. The ± Y side end of the upper electrode 123 is connected to the common electrode line 123A. The common electrode wire 123A connects a plurality of upper electrodes 123 arranged in the X direction, and both ends (± X side ends) of the common electrode wire 123A are connected to a circuit board or the like. It becomes.
The piezoelectric layer 122 is formed of a thin film of a piezoelectric material such as PZT (lead zirconate titanate). As shown in FIG. 2, the protective film 124 may be provided so as to cover the side surface portion of the piezoelectric layer 122.

Here, one ultrasonic transducer Tr is configured by one vibrating portion 112A in the vibrating film 112 and the piezoelectric element 12 provided on the vibrating portion 112A. Therefore, as shown in FIG. 1, a plurality of ultrasonic transducers Tr are arranged in the ultrasonic device 10 along the X direction and the Y direction.
Further, in the ultrasonic device 10 of the present embodiment, the lower electrodes 121 are common to the plurality of ultrasonic transducers Tr arranged in the X direction, and the plurality of ultrasonic transducers Tr arranged in the X direction are used. A 1CH (channel) transmission / reception column Ch is configured. Further, the ultrasonic device 10 having a one-dimensional array structure is configured by arranging a plurality of transmission / reception rows Ch of the 1CH side by side along the Y direction.

In the ultrasonic transducer Tr having such a configuration, the piezoelectric layer 122 expands and contracts by applying a pulse wave voltage of a predetermined frequency between the lower electrode 121 and the upper electrode 123, and the piezoelectric element 12 is provided. The vibrating portion 112A of the vibrating film 112 vibrates at a frequency corresponding to the opening width of the opening 111A and the like. As a result, ultrasonic waves are transmitted from the + Z side (opening 111A side) of the vibrating portion 112A.
Further, when an ultrasonic wave is input to the opening 111A, the vibrating portion 112A vibrates due to the ultrasonic wave, and a potential difference is generated above and below the piezoelectric layer 122. Therefore, it is possible to detect (receive) ultrasonic waves by detecting the potential difference generated between the lower electrode 121 and the upper electrode 123.

(Structure of damper layer 13)
A damper layer 13 is provided on the −Z side of the vibrating film 112.
In the present embodiment, the damper layer 13 covers the entire -Z side of the vibrating film 112 and each piezoelectric element 12 (that is, the surface opposite to the side on which ultrasonic waves are transmitted and received). When viewed from the Z direction, the damper layer 13 has a portion that overlaps with the piezoelectric element 12 adheres to the surface of the piezoelectric element 12, and a portion that does not overlap with the piezoelectric element 12 adheres to the −Z side surface of the vibrating film 112. doing.
The damper layer 13 is made of a material having a Young's modulus of 130 MPa or less (for example, silicone or the like). Further, the thickness dimension (dimension along the Z direction) of the damper layer 13 is 13 μm or more and 25 μm or less.

By the way, in the present embodiment, as described above, ultrasonic waves are transmitted by the vibration of the vibrating portion 112A of the vibrating membrane 112. Specifically, by vibrating the vibrating unit 112A, the vibration of the vibrating unit 112A directly acts on the air to generate a compressional wave, and ultrasonic waves are transmitted.
Here, in the configuration in which the vibrating membrane 112 is vibrated to transmit ultrasonic waves as described above, when the damper layer 13 is not provided, the Q value of the vibrating membrane 112 itself becomes very high, and the transmission / reception control of ultrasonic waves is controlled. Becomes difficult. In addition, the time until the vibration converges (the time during which the reverberation vibration occurs) also becomes long.
Therefore, in the present embodiment, as described above, the above problem is solved by providing the damper layer 13 having a thickness dimension of 13 μm or more and 25 μm or less.

FIG. 3 is a diagram showing the relationship between the thickness dimension of the damper layer 13 and the maximum displacement amount of the vibrating portion 112A when the vibrating portion 112A is vibrated by applying a predetermined periodic drive voltage to the piezoelectric element 12. ..
When the thickness dimension of the damper layer 13 is increased, the vibration amplitude of the vibrating portion 112A is reduced, which lowers the transmission / reception sensitivity of ultrasonic waves. In particular, as shown in FIG. 3, when the thickness dimension of the damper layer 13 exceeds 25 μm, the maximum displacement amount is greatly reduced. When the maximum displacement amount decreases, the transmission sensitivity of ultrasonic waves when a voltage is applied to the piezoelectric element 12 decreases. Further, even when the ultrasonic wave is received, the vibrating portion 112A is less likely to vibrate, so that the receiving sensitivity is also lowered.
On the other hand, when the thickness dimension of the damper layer 13 is 25 μm or less, the maximum displacement amount of the vibrating portion 112A is maintained in the vicinity of 10 μm. That is, when the thickness dimension of the damper layer 13 is 25 μm or less, a displacement amount substantially the same as when the damper layer 13 is not provided can be obtained, and it can be seen that sufficient ultrasonic wave transmission / reception sensitivity can be obtained.

Next, the reverberation vibration when the vibrating unit 112A vibrates will be described.
The ultrasonic device 10 measures the distance from the ultrasonic device 10 to the object by transmitting ultrasonic waves from each ultrasonic transducer Tr and receiving the ultrasonic waves (reflected waves) reflected by the object. It becomes possible to do. However, when there is vibration (reverberation vibration) of the vibrating unit 112A when ultrasonic waves are transmitted from the ultrasonic transducer Tr, when the reflected wave is received, the vibrating unit 112A accompanying the reception of the signal due to the reverberant vibration and the reflected wave. It becomes difficult to distinguish it from the signal due to the vibration of, and the accuracy at the time of receiving ultrasonic waves decreases. In addition, there is an inconvenience that a weak ultrasonic wave due to reverberation vibration is transmitted. In particular, when the ultrasonic device 10 is used as a short-distance sensor or the like for detecting an object at a short distance, the reflected wave may be received during the period when the reverberation vibration as described above remains, and the reverberation vibration is long. It is not desirable to occur for a period of time.

Here, the time until the amplitude becomes 1/10 after transmitting one pulse of ultrasonic waves by the ultrasonic transducer Tr is defined as the pulse width (μsec) due to the reverberation vibration. FIG. 4 is a diagram showing a waveform of reverberation vibration when the damper layer 13 is not provided. FIG. 5 is a diagram showing a waveform of reverberation vibration when the damper layer 13 having a thickness dimension of 20 μm is provided. In FIGS. 4 and 5, the broken line indicates an amplitude that is 1/10 of the maximum amplitude. 4 and 5 are the results of measuring the change in the vibration amplitude of the vibrating unit 112A after transmitting one pulse of ultrasonic waves from the ultrasonic transducer Tr.
As shown in FIG. 4, the pulse width (time until the amplitude becomes 1/10) when the damper layer 13 is not provided is about 200 μsec. On the other hand, as shown in FIG. 5, when the damper layer 13 having a thickness of 20 μm is provided, the pulse width is about 75 μsec, and the period during which reverberation vibration occurs is longer than that when the damper layer 13 is not provided. It can be seen that it is less than 1/2.

Further, FIG. 6 is a diagram showing the relationship between the thickness dimension of the damper layer 13 and the pulse width when the width dimension of the opening 111A is 170 μm, 200 μm, and 260 μm. FIG. 7 is a diagram showing a change in the pulse width when the thickness dimension of the damper layer 13 is 0 in FIG. 6 as a reference (100%).
As shown in FIGS. 6 and 7, by setting the thickness dimension of the damper layer 13 to 13 μm or more, the pulse width can be halved or less regardless of the opening width (ultrasonic frequency) of the opening 111A.
On the other hand, when the thickness dimension of the damper layer 13 is less than 13 μm, the pulse width due to the reverberation vibration becomes long, and the accuracy at the time of transmitting and receiving ultrasonic waves cannot be sufficiently maintained.

That is, by providing the damper layer 13 having a thickness dimension of 13 μm or more and 25 μm or less, the ultrasonic wave transmission / reception sensitivity can be increased, the reverberation vibration can be shortened, and the ultrasonic wave transmission / reception accuracy can be improved. Can be done.

Next, the Young's modulus of the damper layer 13 will be described.
FIG. 8 is a diagram showing the relationship between the Young's modulus of the damper layer 13 and the deformation efficiency of the vibration amplitude of the vibrating portion 112A. In FIG. 8, the deformation efficiency when the damper layer 13 is not provided is set to 100%.
When a material having a Young's modulus of 10 MPa or less is used as the damper layer 13, the vibration amplitude of the vibrating portion 112A is almost unchanged as compared with the case where the damper layer 13 is not provided, as shown in FIG. That is, when transmitting ultrasonic waves, ultrasonic waves having a high sound pressure can be transmitted, and when the ultrasonic waves are received, the vibration of the vibrating unit 112A can be increased, so that a received signal with a high signal level can be obtained.
When the Young's modulus is further increased from 10 MPa, the vibration efficiency of the vibrating portion 112A decreases as shown in FIG. 8, and when it exceeds 500 MPa, the vibration efficiency of the vibrating portion 112A falls below 50%.
As for the transmission / reception sensitivity of ultrasonic waves, it is preferable to suppress the decrease in vibration efficiency to 50% or less. Therefore, the Young's modulus of the damper layer 13 is preferably 500 MPa or less. As the material of such a damper layer 13, for example, silicone rubber, various rubber materials, polyethylene and the like can be used, and it is more preferable to use silicone rubber and various rubber materials having a Young's modulus of 10 MPa or less.

[Action and effect of this embodiment]
In the ultrasonic device 10 of the present embodiment, the damper layer 13 is provided in contact with the vibrating portion 112A provided with the piezoelectric element 12, and the thickness dimension of the damper layer 13 is 13 μm or more and 25 μm or less.
By providing such a damper layer 13, the Q value of the vibrating unit 112A can be lowered, and the transmission / reception control of ultrasonic waves in the ultrasonic device 10 can be easily performed. That is, when the damper layer 13 is not provided in the vibrating unit 112A, the responsiveness of each ultrasonic transducer Tr becomes excessively high, so that even if a slight disturbance vibration is input to the ultrasonic device 10, for example, the vibrating unit Inconveniences such as vibration of 112A and output of a received signal occur. In this case, the received signal is output even though the ultrasonic wave is not input. On the other hand, by providing the damper layer 13, the Q value of the vibrating unit 112A is lowered, and it becomes possible to appropriately control the transmission and reception of ultrasonic waves.
Further, in the present embodiment, since the thickness dimension of the damper layer 13 is 13 μm or more, reverberation vibration when the ultrasonic transducer Tr is driven can be suppressed as shown in FIGS. 6 and 7. As a result, unintended ultrasonic wave transmission due to reverberation vibration, reception of reflected waves during reverberation vibration, and the like can be suppressed, and the transmission / reception accuracy of ultrasonic waves can be improved.
Further, since the thickness dimension of the damper layer 13 is 25 μm or less, it is possible to suppress a decrease in the maximum displacement amount of the vibrating portion 112A as shown in FIG. As a result, when transmitting ultrasonic waves, it is possible to transmit ultrasonic waves having a high output value, and when receiving reflected waves, it is possible to obtain a received signal having a high signal level, and it is possible to increase the transmission / reception sensitivity of ultrasonic waves.
That is, in the present embodiment, the transmission / reception sensitivity of ultrasonic waves by the ultrasonic device 10 can be increased, the ultrasonic wave transmission / reception processing can be performed with high accuracy, and the control related to the transmission / reception of ultrasonic waves can be easily performed. can.

In this embodiment, the Young's modulus of the damper layer 13 is 150 MPa or less. Therefore, the inconvenience that the vibration of the vibrating portion 112A is hindered by the damper layer 13 is suppressed, and as shown in FIG. 8, the deformation efficiency of the vibrating portion 112A can be maintained at 50% or more. As a result, the transmission / reception sensitivity of ultrasonic waves can be increased.

In the present embodiment, the piezoelectric element 12 is provided on the −Z side surface of the vibrating portion 112A, and the damper layer 13 is formed so as to cover the vibrating portion 112A and the piezoelectric element 12. In such a configuration, the piezoelectric element 12 is covered with the damper layer 13, and inconveniences such as burning due to adhesion of water droplets to the piezoelectric element 12 can be suppressed, and the piezoelectric element can be suitably protected.

In the present embodiment, the ultrasonic device 10 vibrates the vibrating unit 112A to transmit ultrasonic waves from the vibrating unit 112A to the opening 111A side and receive the ultrasonic waves input from the opening 111A side. The damper layer 13 is provided on the −Z side opposite to the + Z side, which is the transmission / reception direction of ultrasonic waves of the vibrating unit 112A. Therefore, in the ultrasonic wave transmission / reception process, the damper layer 13 does not intervene in the path direction of the ultrasonic wave, and the ultrasonic wave is not attenuated. Therefore, when transmitting ultrasonic waves, it is possible to output ultrasonic waves having a large output (amplitude), and when receiving ultrasonic waves, the amount of displacement of the vibrating portion 112A due to the reflected wave can be increased, and a received signal with a high signal level can be obtained. Can be done.

[Second Embodiment]
Next, the second embodiment will be described. In the second embodiment, a distance sensor as an example of the ultrasonic measuring device including the ultrasonic device 10 described in the first embodiment will be described.
FIG. 9 is a diagram showing a schematic configuration of the distance sensor 100 according to the present embodiment.
As shown in FIG. 9, the distance sensor 100 of the present embodiment includes an ultrasonic device 10 and a control unit 20 that controls the ultrasonic device 10. The control unit 20 includes a drive circuit 30 for driving the ultrasonic device 10 and a calculation unit 40. In addition, the control unit 20 may also include a storage unit that stores various data, various programs, and the like for controlling the distance sensor 100.

The drive circuit 30 is a driver circuit for controlling the drive of the ultrasonic device 10. For example, as shown in FIG. 9, the drive circuit 30 includes a reference potential circuit 31, a switching circuit 32, a transmission circuit 33, a reception circuit 34, and the like.
The reference potential circuit 31 is connected to the upper electrode terminal 123P and applies a reference potential (for example, -3V or the like) to the upper electrode terminal 123P.
The switching circuit 32 is connected to each lower electrode terminal 121P, a transmitting circuit 33, and a receiving circuit 34. The switching circuit 32 is composed of a switching circuit, and is a transmission connection for connecting each of the lower electrode terminals 121P and the transmission circuit 33, and a reception for connecting each of the lower electrode terminals 121P and the reception circuit 34. Switch the connection.

The transmission circuit 33 is connected to the switching circuit 32 and the calculation unit 40, and when the switching circuit 32 is switched to the transmission connection, a pulse waveform drive signal is sent to each ultrasonic transducer Tr under the control of the calculation unit 40. Is output, and ultrasonic waves are transmitted from the ultrasonic device 10.
The receiving circuit 34 is connected to the switching circuit 32 and the arithmetic unit 40, and when the switching circuit 32 is switched to the receiving connection, the received signal from each lower electrode 121 is input. The receiving circuit 34 includes, for example, a linear noise amplifier, an A / D converter, and the like, and converts an input received signal into a digital signal, removes noise components, amplifies to a desired signal level, and the like. After performing signal processing, the processed received signal is output to the calculation unit 40.

The calculation unit 40 is composed of, for example, a CPU (Central Processing Unit) or the like, controls the ultrasonic device 10 via a drive circuit 30, and causes the ultrasonic device 10 to perform ultrasonic wave transmission / reception processing.
That is, the calculation unit 40 switches the switching circuit 32 to the transmission connection, outputs a drive signal from the transmission circuit 33 to each ultrasonic transducer Tr of the ultrasonic device 10, and transmits ultrasonic waves. Further, the calculation unit 40 switches the switching circuit 32 to the reception connection immediately after transmitting the ultrasonic wave. As a result, when the reflected wave is received by the ultrasonic device 10, the received signal is input to the calculation unit 40 via the receiving circuit 34. Then, the calculation unit 40 uses the time from the transmission timing at which the ultrasonic wave is transmitted from the ultrasonic device 10 to the reception of the received signal and the sound velocity in the air by the ToF (Time of Flight) method. The distance from the ultrasonic device 10 to the object is calculated.

The distance sensor 100 of the present embodiment as described above includes the ultrasonic device 10 described in the first embodiment. As described above, the ultrasonic device 10 is provided with a damper layer 13 having a thickness dimension of 13 μm or more and 25 μm or less on the vibrating film 112, so that the ultrasonic device 10 maintains high ultrasonic transmission / reception sensitivity. At the same time, it is possible to transmit and receive highly accurate ultrasonic waves in which reverberation vibration is suppressed, and control related to the transmission and reception of ultrasonic waves becomes easy.
Therefore, the control unit 20 can easily control the ultrasonic wave transmission / reception processing of the ultrasonic wave device 10, and the ultrasonic wave is based on the highly accurate ultrasonic wave transmission / reception result obtained by the ultrasonic wave device 10. The distance from the device 10 to the object can be calculated with high accuracy.

[Modification example]
It should be noted that the present invention is not limited to the above-described embodiments and modifications, and the configuration obtained by appropriately combining modifications and improvements within the range in which the object of the present invention can be achieved, and by appropriately combining the embodiments, etc., is the present invention. It is included in.

For example, in the first embodiment, the ultrasonic device 10 transmits ultrasonic waves from the opening 111A side of the element substrate 11, receives the ultrasonic waves input to the opening 111A, and the damper layer 13 is a vibrating film. The configuration is such that the 112 is provided on the surface opposite to the substrate main body 111, but the present invention is not limited to this.
10 and 11 are cross-sectional views showing another example of the ultrasonic device.
For example, in the ultrasonic device 10A shown in FIG. 10, the surface of the element substrate 11 opposite to the opening 111A (the surface on which the piezoelectric element 12 is provided) is the surface for transmitting and receiving ultrasonic waves. That is, in the ultrasonic device 10A, ultrasonic waves are transmitted from the vibrating film 112 to the −Z side (the side opposite to the substrate main body 111), and the ultrasonic waves input from the −Z side are received by the vibrating unit 112A. .. In the ultrasonic device 10A having such a configuration, as shown in FIG. 10, the damper layer 13 is preferably provided in the opening 111A.
Further, in this case, as shown in FIG. 11, the thickness dimension of the substrate main body 111 may be the same as the thickness dimension of the damper layer 13.

In the first embodiment, an example in which the Young's modulus of the damper layer 13 is composed of a material of 150 MP or less is shown, but more preferably, it is 10 MPa or less, and specifically, it is composed of silicone or various rubber materials. Is more preferable.

In the first embodiment, the piezoelectric element 12 is exemplified as the vibrating element that vibrates the vibrating portion 112A of the vibrating film 112, but the present invention is not limited thereto.
For example, a substrate facing the vibrating region (vibrating portion) of the vibrating membrane via an air gap may be provided, and electrodes may be provided on each of the vibrating portion and the substrate. In such a configuration, by applying a periodic drive voltage between the electrode provided on the vibrating portion and the electrode provided on the substrate, the vibrating portion is attracted to the substrate side by electrostatic attraction and vibrates. , Sends ultrasonic waves. Further, when the ultrasonic wave is received, the vibrating portion is vibrated, so that the capacitance between the electrodes fluctuates. That is, the reception of ultrasonic waves is detected by detecting the fluctuation of the capacitance.
Further, in this configuration, the ultrasonic wave is output to the side opposite to the substrate of the vibrating part. Therefore, a damper layer in contact with the vibrating portion is provided between the vibrating portion and the substrate (air gap). As a result, as in the above embodiment, the transmission / reception sensitivity of ultrasonic waves can be maintained high, the reverberation vibration can be suppressed, and the control related to the transmission / reception of ultrasonic waves can be easily performed.

In the first embodiment, the ultrasonic device 10 that transmits ultrasonic waves into the air and receives the ultrasonic waves propagated from the air is illustrated, and the damper layer 13 is used as the transmission direction of the ultrasonic waves of the vibrating film 112. Was configured to be provided on the opposite surface.
On the other hand, for example, when ultrasonic waves are transmitted into water or the like, a damper layer 13 made of silicone rubber or the like may be provided in the direction of ultrasonic wave transmission in the vibrating membrane 112. That is, as long as the damper layer 13 has an acoustic impedance similar to that of the medium for propagating the ultrasonic waves, it may be provided in the transmission direction of the ultrasonic waves.

In the second embodiment, the distance sensor 100 has been illustrated as an example of the ultrasonic measuring device, but the present invention is not limited to this. For example, it can be applied to an ultrasonic measuring device or the like that measures an internal tomographic image of a structure according to the result of transmitting and receiving ultrasonic waves.

In addition, the specific structure at the time of carrying out the present invention may be configured by appropriately combining each of the above embodiments and modifications as long as the object of the present invention can be achieved, or may be appropriately changed to another structure or the like. You may.

10, 10A ... Ultrasonic device, 11 ... Element substrate, 12 ... Piezoelectric element, 13 ... Damper layer, 20 ... Control unit, 30 ... Drive circuit, 40 ... Calculation unit, 100 ... Distance sensor (ultrasonic measuring device), 111 ... Substrate body, 111A ... Opening, 111B ... Wall, 112 ... Vibrating film, 112A ... Vibrating part, 121 ... Lower electrode, 122 ... Piezoelectric layer, 123 ... Upper electrode, Tr ... Ultrasonic transducer.

Claims (4)

A vibrating membrane having a vibrating region that can be vibrated by a vibrating element,
A damper layer provided so as to cover the vibration region of the vibration membrane is provided.
The thickness dimension of the damper layer state, and are more 25μm or less 13 .mu.m,
The ultrasonic device is characterized in that the damper layer is made of a material having a Young's modulus of 150 MPa or less. In the ultrasonic device according to claim 1,
The vibrating element is a piezoelectric element including a lower electrode provided on one surface of the vibrating film, a piezoelectric layer laminated on the lower electrode, and an upper electrode laminated on the piezoelectric layer.
An ultrasonic device characterized in that the damper layer is provided on the one surface of the vibrating membrane on which the piezoelectric element is provided. In the ultrasonic device according to claim 1 or 2.
The direction in which ultrasonic waves are transmitted when the vibrating region is vibrated by the vibrating element is set as the first direction.
An ultrasonic device characterized in that the damper layer is provided on a surface of the vibrating membrane opposite to the first direction. The ultrasonic device according to any one of claims 1 to 3 , and the ultrasonic device.
A control unit that controls the ultrasonic device and
An ultrasonic measuring device characterized by being provided with.

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